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Unexpected chirality transition and inversion mediated by dissolution-aggregation and the odd-even effect.

Yafei Ma¹, Xiaoxiao Cheng¹, Haotian Ma¹

¹State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Jiangsu Engineering Laboratory of Novel Functional Polymeric Materials, Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, College of Chemistry, Chemical Engineering and Materials Science, Soochow University Suzhou 215123 Jiangsu China weizhang@suda.edu.cn xxcheng@suda.edu.cn.

Chemical Science

|December 12, 2022

Summary

Researchers achieved controlled chirality transitions in azobenzene polymers. An odd-even effect was discovered, regulating helical orientation in polymer assemblies for precise chiral control.

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Area of Science:

Polymer Science
Supramolecular Chemistry
Chirality Studies

Background:

Hierarchical chirality is common in biological systems but difficult to control in synthetic polymers.
Side-chain azobenzene polymers offer potential for tunable chiral properties.

Purpose of the Study:

To investigate chiroptical transitions and inversion phenomena in side-chain azobenzene polymers.
To explore the relationship between polymer structure and supramolecular chirality.
To establish control over chiral transitions in polymer systems.

Main Methods:

Synthesis of side-chain azobenzene polymers (PAzo-l/d-m) with varying chiral center to azobenzene distances (m).
Chiroptical spectroscopy to analyze transitions and inversions.
Heating-assisted reassembly and aggregation studies.
Investigation of exciton coupling and aggregation states (H- to J-aggregation).

Main Results:

Observed multiple chiroptical transitions and inversion phenomena in PAzo-l/d-m polymers.
Demonstrated an in situ macromolecular-to-supramolecular chirality transition and inversion for m=3.
Revealed exciton-coupling induced multiple chiroptical inversion driven by H- to J-aggregation.
Established an odd-even effect to control supramolecular helical orientation (left/right-handedness).

Conclusions:

Precise control over hierarchical chirality transitions is achievable in side-chain azobenzene polymers.
The distance from the chiral center to the azobenzene unit significantly impacts chiroptical behavior.
The odd-even effect provides a novel strategy for directing supramolecular chirality in polymer assemblies.